(Chemi symbol Ca) A chemical element with atomic number of 20 and a molar mass of 40.08 grams.
In terms of physical properties, it's melting point is 1115°K or 842 °C (1548 °F) and boiling point is 1757 or 1484 °C (2703 °F). It's density is 1550 kg/m3 and it's molar volume is 26.20 cm3.
In terms of chemical properties: it is a group 2 metal (or Alkaline Earth Metal) with 2 electrons in the outermost valency shell. As well as 2, 8, and 8 electrons in it's 1st, 2nd and 3rd shell respectively, which are not used in chemical bonding.
Calcium ions typically have a charge of 2+ and exist in aqueous calcium salt solutions. Calcium exists, chemically bound, in human bones to provide strength as well as in Marble structures.
Calcium is not naturally found in its chemical form due to it's relatively high reactivity. However, it is the 5th most abundant element in the earth's crust. Elemental Calcium can be extracted through a process of smelting and electrolysis. It reacts spectacularly in water or when ignited in an oxygen rich atmosphere.
Calcium used for experimentation in labs is usually a dull greyish colour because the surface has been oxidised by atmospheric oxygen.
*Anyone who has bothered reading this far is truly a nerd (or someone doing an assignment)*

I am the science man who has concisely defined the chemical element calcium in his own words.

mom: you have to get a WHAT?!?!
daughter: *sobbing* a calcium abortion
mom: what i want to know is how you got calcium in the first place
daughter: well, me and johnny were drinking milkshakes...and we didn't remember to use our bendy straws *starts sobbing again*